Metabolic exchange is a universal phenomenon. It is essential to every organism, from those as simple as bacteria to complex higher eukaryotes such as humans. While metabolic exchange enables cooperation and coordination between the ~70 trillion cells in an average human being, even unicellular organisms rely on metabolic exchange to adapt to environmental stress and form biofilms. Cellular communication allows stem cells to differentiate, cancer cells to proliferate, neurons to fire, bacteria to sense a quorum and pathogens to survive in human hosts. The chemical diversity of the molecules used for communication is extraordinary, and includes small ions such as calcium, small molecules such as secondary metabolites, fatty acids, peptides, but also carbohydrates, proteins and nucleic acids. Despite the universal nature of metabolic exchange, there are few methods that can characterize the communication between cells in a systematic and sensitive fashion, let alone real-time. In this proposal, our focus will be on the application and adaptation of desorption electrospray mass spectrometry to enable the real-time live cell detection and the characterization and visualization of metabolic exchange in important biological processes. We aim to accomplish this in both a spatial as well as temporal fashion. These tools will improve our understanding of secreted biomarkers, microbiome-human cell interactions and understanding the complexities of infectious disease that derive from the cooperation between different types of cells (e.g. Bacilli with macrophages, neutrophils or T-cells) and interkingdom communication. Ultimately it may drive the development of new therapeutic strategies or interventions based on paradigms involving inter-cellular metabolic communication in a system wide fashion. PUBLIC HEALTH RELEVANCE: This proposal aims to develop real-time monitoring of molecular entities involved in metabolic exchange of pathogen-immunological cell populations. Our ability to visualize metabolic exchange between different cell populations could lead to new therapeutic paradigms.